Michael Morse, right, was celebrating with Jason Bay after Morse’s two-run homer in the first inning — his fifth in seven games — but he struck out his next four times up.

Dayan Viciedo hit a walkoff homer in the 10th off Seattle's Kameron Loe to help Chicago claim the series.

CHICAGO — Michael Morse says he’s emerging from this first, power-laden week feeling like he needs to ease up on the aggressiveness and just relax.

And that’s a message Morse figures the rest of his Mariners teammates and any skittish fans might want to adhere to as well. As disappointed as the Mariners were following this 4-3 loss in 10 innings Sunday to the Chicago White Sox, they insist it’s still far too early in the season to get worked up about too much.

“We’re not getting the base hits as much right now and no one’s really clicked yet,” said Morse, who hit his fifth home run in seven games in the first inning, but struck out his final four times up. “It’s early and there’s a lot of baseball left.”

Dayan Viciedo became the latest in a long line of White Sox to deal the Mariners a walkoff defeat on a home run at U.S. Cellular Field. The Mariners haven’t won a series here since 2007 and won’t this season after Viciedo lifted the crowd of 18,708 to their feet in the 10th with a no-doubt solo shot to left off Kameron Loe on a sinker that didn’t sink.

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That handed the Mariners their fourth loss in the last five games on a road trip that finished 3-4 after a 2-0 start.

“I fell behind 2-0, and I tried to get back in the count and I just left a sinker up,” Loe said. “I would have preferred for it to be away. It came back over the middle of the plate and he hit it well.”

The blast was the first game-ending homer of Viciedo’s career.

“You pipe it down the middle 2-0 to any of these big-league hitters and they’re probably going to put a big swing on it,” Loe said.

The Mariners have lost eight consecutive series at this ballpark since 2007 and are 4-21 here over that span. Chicago has won 13 its last 15 against the Mariners overall and 26 of 31 since the start of 2010.

Many of the Mariners’ losses here have come via late home runs. Alex Rios went deep for the third game in a row in the seventh inning off Hisashi Iwakuma to erase a 3-2 lead for the Mariners and send these teams to their second extra-inning affair of this series. The Mariners won the opener 8-7 in 10 innings Friday night, but dropped the final two.

Adam Dunn also hit a home run for the White Sox on Sunday, a two-run shot off Iwakuma in the first inning to tie the score at 2-2.

Iwakuma went on to retire the next 16 batters in a row until Rios went deep. That bought the Mariners more time to generate offense, but they went 0-for-7 with runners in scoring position.

Morse came up three times with a runner at second base and went down swinging on all three occasions, including in the 10th against White Sox closer Addison Reed. Things had started off far better for Morse when he connected for a two-run blast to left in the first inning off White Sox southpaw starter Chris Sale.

That made Morse the only Mariners hitter other than Ken Griffey Jr. in 1997 to hit five home runs in the first week. Griffey wound up with six in the first seven games that year.

Kendrys Morales added his first Mariners home run in the sixth off Sale to put Seattle ahead 3-2. Morales also had a double, a single and was walked intentionally on a 3-for-4 day.

But like Morse, the Mariners started quickly on offense and just couldn’t finish.

“I think we’re definitely underachieving what we’re capable of doing,” Morse said. “But we haven’t played what, a week of baseball? I think we’ve showed some good signs of what we’re capable of doing.”

And the key now, he added, is for everyone to just relax and get their feet underneath them. Morse has struck out nine times his last 18 at-bats and says he needs to calm his bat.

“They’re feeding off my aggressiveness right now,” he said. “I just need to relax a little bit and zone up a little more. Just stay aggressive, but under control. I’m kind of swinging out of the zone a little bit. But like I said, it’s way early and there’s a lot of baseball left.”

Mariners manager Eric Wedge said playing 14 in a row to open the season without a break is a tough schedule for any club. He said his team looks forward to getting home for tomorrow’s Safeco Field opener against the Houston Astros.

“It’s the first week and there are some good things that have happened and some things we need to get better with,” Wedge said. “We need to settle in offensively. We know we’re going to be a good offensive club. But we need to settle in offensively, both different individuals and collectively. That will take some of the pressure off the pitching staff.”